Dielectric Measurement Protocols on Medium Voltage Cable Joints at Variable Temperatures

In recent years, the increasing frequency of extreme heat events, particularly in urban areas, has raised concerns about the reliability of Medium Voltage (MV) underground distribution systems. Among the components most affected by higher and higher temperatures, cable joints have emerged as particularly susceptible due to partial discharge (PD) phenomena with premature faults. This paper presents a structured test protocol to evaluate the dielectric performance of MV joints under combined thermal and electrical stress in a controlled laboratory setting. The methodology includes diagnostic measurements such as PD activity, dielectric loss angle (tanδ), and insulation resistance (IR), carried out under both ambient and high temperatures (via thermostatic chamber). The aim is to correlate joint insulation behaviour with operating temperatures, identify early degradation signs, and support the qualification of joint technologies for use in a more resilient distribution grid.